Consolidated Statements Of Income (Loss) And Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2019		Jun. 30, 2018		Jun. 30, 2019		Jun. 30, 2018
OPERATING REVENUES
Earned premiums	$ 1,199,461		$ 1,148,184		$ 2,403,438		$ 2,299,205
Net investment income	111,831		105,387		226,013		213,403
Net realized investment gains (losses)	(67)		(7,642)		614		(8,588)
Change in fair value of equity securities	425,720		112,891		1,037,230		(9,161)
Net investment gains (losses)	425,653		105,249		1,037,844		(17,749)
Products revenues	501,676		472,323		850,470		766,459
Services and other revenues	200,495		155,870		393,839		301,166
Total Operating Revenues	2,439,116		1,987,013		4,911,604		3,562,484
OPERATING EXPENSES
Losses and loss adjustment expenses	678,120		599,178		1,365,866		1,214,296
Underwriting, acquisition and insurance expenses	462,316		451,570		917,528		875,960
Products expenses	425,138		450,585		744,564		720,282
Services and other expenses	170,796		129,854		345,402		262,287
Amortization of intangible assets	36,300	[1]	29,641	[2]	76,968	[3]	58,464	[4]
Impairment of goodwill and intangible assets	0		14,904		0		14,904
Total Operating Expenses	1,772,670		1,675,732		3,450,328		3,146,193
Operating Income	666,446		311,281		1,461,276		416,291
Interest expense	41,267		36,702		81,557		76,761
Net foreign exchange gains	(25,015)		(86,158)		(3,151)		(64,044)
Income Before Income Taxes	650,194		360,737		1,382,870		403,574
Income tax expense	143,711		81,150		298,874		189,581
Net Income (Loss)	506,483		279,587		1,083,996		213,993
Net income attributable to noncontrolling interests	9,185		1,356		10,271		68
Net Income to Shareholders	497,298		278,231		1,073,725		213,925
OTHER COMPREHENSIVE INCOME (LOSS)
Net holding gains (losses) arising during the period	128,467		(98,145)		280,798		(215,067)
Reclassification adjustments for net gains (losses) included in net income	803		(5,891)		557		(5,077)
Change in net unrealized gains on available-for-sale investments, net of taxes	129,270		(104,036)		281,355		(220,144)
Change in foreign currency translation adjustments, net of taxes	(3,749)		(10,450)		(1,372)		(5,497)
Change in net actuarial pension loss, net of taxes	515		568		1,876		1,232
Total Other Comprehensive Income (Loss)	126,036		(113,918)		281,859		(224,409)
Comprehensive Income (Loss)	632,519		165,669		1,365,855		(10,416)
Comprehensive income attributable to noncontrolling interests	9,189		1,333		10,280		87
Comprehensive Income (Loss) to Shareholders	$ 623,330		$ 164,336		$ 1,355,575		$ (10,503)
NET INCOME PER SHARE
Basic (in dollars per share)	$ 36.10		$ 20.01		$ 78.91		$ 15.75
Diluted (in dollars per share)	$ 36.07		$ 19.97		$ 78.85		$ 15.72

[1] Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to any other reportable segments.

[2] Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to any other reportable segments.

[3] Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to any other reportable segments.

[4] Segment profit for the Markel Ventures segment includes amortization of intangible assets attributable to Markel Ventures. Amortization of intangible assets is not allocated to any other reportable segments.